This invention is generally directed to processes for the preparation of photogenerating compositions, and more specifically, the present invention is directed to bisazo photogenerating pigments prepared by annealing methods. In one embodiment of the present invention there are provided economical processes for the preparation of bisazo photogenerating pigments by the reaction of diaminofluorenone with anilide couplers, such as the anilides of hydroxy benzocarbazolecarboxylic acids, followed by annealing. The pigments resulting from the processes of the present invention can be selected for layered photoconductive imaging members with improved xerographic properties, inclusive of high charge acceptance, low dark decay, high photosensitivity, including photosensitivity in the wavelength regions of from about 400 to about 800 nanometers, enabling their selection for electrophotographic, especially xerographic imaging systems, LED printers, and diode laser printers which are usually senstive to wavelengths of from about 600 to about 800 nanometers. In one embodiment of the invention of the present application there are provided imaging members with photoconductive layers comprised of the bisazo pigments prepared by the annealing processes illustrated herein, and charge or hole transport layers, especially those comprised of aryl amines, which members are sensitive to light in the wavelength region of from about 400 to about 800 nanometers. The resulting members are responsive to visible light, and near infrared illumination orginating from laser printing apparatuses wherein, for example, gallium arsenide diode lasers are selected. The photoresponsive imaging members of the present invention can also, for example, contain situated between a photogenerating layer and a hole transporting layer, or situated between a photogenerating layer and a supporting substrate with a charge, especially hole, transport layer in contact with the photogenerating layer, a photoconductive composition comprised of the bisazo photogenerating pigments obtained by the processes illustrated herein.
Many processes are known for the preparation of azo photogenerating pigments, such as azotization and coupling, reference U.S. Pat. No. 3,898,084. Examples of aromatic amines selected for the preparation of azo photogenerating pigments include 2,7-diaminofluorenone, and imaging members thereof, reference for example U.S. Pat. Nos. 4,797,337; 4,830,942; 4,822,705; 4,596,754; 4,618,672; 4,618,672; 4,481,271; 4,400,455; 4,390,608; 4,327,178; 4,314,015; 4,299,015; 4,299,896 and 4,551,404.
In U.S. Pat. No. 4,916,039 there are disclosed photoconductors with charge generating pigments comprised of certain azo compounds, reference the formula illustrated in the Abstract of the Disclosure, and in column 3. The aforementioned azo pigments are prepared by the coupling reaction of certain carbazole derivatives of Formula VI, with diazonium salts, reference columns 6 and 7. The coupling reaction is accomplished by dissolving the diazonium salts and a coupler in an organic solvent, such as DMF and DMSO, and adding dropwise thereto an alkaline aqueous solution at a temperature of from about -10.degree. to about 40.degree. C., see column 7 for example. A similar coupling reaction is disclosed in U.S. Pat. No. 4,925,758 wherein, for example, there are selected costly couplers as compared to the more economical couplers that may be selected for the processes of the present invention.
In a patentability search report, the following U.S. Pat. Nos. were recited: 4,299,896 which discloses, for example, that disazo pigments can be prepared by first diazotizing 2,7-diaminofloren-9-one and reacting the product with a coupler such as naphthol AS; a similar teaching is present in 4,314,015; and 4,666,810, imaging members with azo pigments prepared subjecting a diazonium salt of the amino groups to aqueous coupling with a corresponding coupler in the presence of an alkali, and the like, see column 3 to 7 for example, and note the synthesis Examples. Imaging members with certain bisazo pigments are known, reference for example U.S. Pat. No. 3,898,084, which discloses, for example, the azo pigment chlorodiane blue in a photoconductive imaging member.
U.S. Pat. No. 3,574,181 discloses disazo compounds useful as coloring agents. Composite electrophotographic photosensitive materials containing various azo compounds are disclosed in U.S. Pat. No. 4,618,672, wherein bisazo compounds particularly suitable for use in the charge generating layer of a layered electrophotographic photoconductor are illustrated. Similarly, an article by M. Hashimoto entitled "Electrophotographic Sensitivity of Fluorenone Bisazo Pigments," Electrophotography, Vol. 25, No. 3 (1986), discloses disazo compounds as charge generating materials in electrophotographic layered photoreceptors. Further, Japanese Patent Kokai No. 54-20736 discloses disazo pigments as constituents in electrophotographic processes. Japanese Patent 58-177955 also discloses many disazo compounds suitable for use in the photosensitive layer of an electrophotographic device.
U.S. Pat. No. 4,713,307, the disclosure of which is hereby totally incorporated by reference, discloses photoconductive imaging members containing a supporting substrate, certain azo pigments as photogenerating materials, and a hole transport layer that preferably contains an aryl diamine compound dispersed in an inactive resinous binder.
U.S. Pat. No. 4,797,337, the disclosure of which is totally incorporated herein by reference, discloses a photoconductive imaging member comprising a supporting substrate, a hole transport layer, and a photogenerating layer comprising specific disazo compounds.
Additional references illustrating layered organic electrophotographic photoconductor elements with azo, bisazo, and related compounds include U.S. Pat. Nos. 4,390,611, 4,551,404, 4,596,754, Japanese Patent 60-64354, U.S. Pat. Nos. 4,400,455, 4,390,608, 4,327,168, 4,299,896, 4,314,015, 4,486,522, 4,486,519, 4,555,667, 4,440,845, 4,486,800, 4,309,611, 4,418,133, 4,293,628, 4,427,753, 4,495,264, 4,359,513, 3,898,084, 4,830,944, 4,820,602, and Japanese Patent Publication 60-111247.
In U.S. Pat. No. 4,833,052, the disclosure of which is totally incorporated herein by reference, there are illustrated certain bisazo photoconductive imaging members. Examples of bisazo compounds disclosed in this patent include those of the formulas as illustrated in column 4, such as 4,4'-bis(1"-azo-2"-hydroxy-3"-naphthanilide)-1,1'-dianthraquinonylamine.
A number of the azo photogenerating pigments of the aforementioned patents are prepared by known coupling reactions, however, these patents appear to be silent with respect to an annealing process, the invention of the present application, which process enables, for example, the removal of water, in some instances solvents such as DMF, and thus avoiding the problem of the formation of undesirable complexes of water with functional groups present on the photogenerating pigment. With the processes of the present invention, there are also enabled imaging members with photogenerating pigments that possess improved xerographic characteristics, and wherein relatively economical couplers can be selected.